Large studies were completed on CD171 and PD-L1. The latter study supported development as PD-L1 as a clinical marker in the Laboratory of Pathology. PD-L1 is normally expressed only in placental trophoblasts and weakly in nerves, probably by Schwann cells. PD-L1 is consistently expressed in trophoblastic neoplasms, including choriocarcinoma, placental site trophoblastic tumor, and trophoblastic elements of mixed germ cell tumors. Frequent expression was also confirmed in Hodgkin lymphoma, anaplastic large cell lymphoma, and squamous cell carcinomas. In gastrointestinal carcinomas, expression was more prevalent in tumors with mismatch repair-deficiency and EBER-positivity. Study of CD171 demonstrated affinity for schwannian tumors and rare expression in GIST, which differed from a previous study. Due to its very rare expression in GIST, CD171 was not found to be useful prognostic marker for GIST, which differed from the results of a previous study. Large studies of Sox10 and brachyury were also completed. These markers support clinical diagnosis and a number of protocols by offering more precise tumor classification. We also established that nuclear beta-catenin expression is a typical and potentially diagnostic feature for intranodal palisaded myofibroblastoma and sinonasal hemangiopericytoma/glomangiopericytoma, both of which also have corresponding CTNNB1 mutations. We also analyzed pediatric and retroperitoneal GISTs and currently study mutations and fusion as tumor progression factors in GIST. We collaborate with NIH investigator Karel Pacak on biology, pathology, and immunotherapy of paragangliomas.